Lip extender for loading dock levelers

ABSTRACT

A lip extender for use with a loading dock leveler. The lip extender includes a lower link connected at its lower end to the base plate of the leveler and a toggle arm connected at its upper end beneath the lip. The opposite ends of the toggle arm and lower link are pivotally connected together. Upward movement of the hinge connection between the bridge plate and lip moves them both upwardly to a cocked position to which they are supported by the toggle arm and lower link, which pivot into an over-center position. Downward force exerted on the upper part of the bridge plate causes a cam follower carried by the pivotal connection between the toggle arm and lower link to engage a cam surface mounted beneath the bridge plate. A coil spring mounted about the lower pivotal point of the lower link exerts pressure against the lower link, thereby counter-balancing the weight of the lip and bridge plate during pivotal movement of the lower link in either direction.

REFERENCE TO RELATED APPLICATION

This application is a continuation-in-part of our co-pending applicationSer. No. 577,754 filed May 15, 1975, now U.S. Pat. No. 3,974,537.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to a device for extending the lip of a loadingdock leveler for movement of the lip into the rear of a truck disposedadjacent to the dock, and counter-balancing the weight of the loadingdock leveler for ease of operation.

2. Description of the Prior Art

Dock leverlers of the type now in use comprise a vertically directedbase plate which is permanently attached to the dock, a bridge platewhich is pivotally attached along one edge thereof to the upper edge ofthe base plate, and a lip which is pivotally attached to the oppositeedge of the bridge plate.

At the present time, it is necessary for the operator to bend over theedge of the dock, catch the bottom edge of the lip with a hook or chaindevice and then lift the lip and swing it out into a horizontalposition. Since the operator is bending over the edge of the dock, thereis no firm support directly beneath him. The operation requires asubstantial amount of bending and twisting of the back, frequentlyresulting in back injuries which are harmful to the operator and costlyto the employer.

There is no device in use at the present time which gives substantialassistance in lifting the lip and/or in extending the lip to itsoperating position.

SUMMARY OF THE INVENTION

It is a primary object of the present invention to provide a lipextender and counter-balance mechanism for loading dock levelers whicheliminates the necessity for the operator to lift the lip separatelyfrom the bridge plate lifting operation and which thereafterautomatically extends the lip into its operating position without anylifting or bending action by the operator. In addition, the mechanismapplies a counter-balancing force to the lip of the leveler which tendsto lock the bridge plate and lip into a flat position when extended,allowing the leveler to be adjusted to provide lighter, easier operationthan has ever before been possible.

In essence, the invention contemplates a lip extending device whichautomatically moves into operating position when the bridge plate pintlepin is lifted. The device lifts the lip into an elevated angularposition with respect to the bridge plate and holds it securely in suchposition. Downward force exerted upon the bridge plate by the foot ofthe operator causes the lip to raise and extend automatically into ahorizontal position overlying the rear edge of the truck simultaneouslywith movement of the bridge plate into a horizontal position. When theleveler is horizontally overlying the rear of the truck, the lipextender mechanism automatically allows the leverler to drop onto thetruck bed, while locking the bridge plate and lip in a horizontalposition to prevent buckling and unwanted removal from the truck, whichoccurs with present state of the art dock levelers.

With existing levelers, jostling of the bridge plate may result in thespring causing the bridge plate to rise, carrying the lip along with it.With the present invention, this cannot occur because the spring exertstension against the lip as well as the bridge plate.

The present application relates to an improvement over our co-pendingapplication Ser. No. 577,754, now U.S. Pat. No. 3,974,537 in that itprovides a coil spring which counter-balances the weight of the lio andhinge plate during pivotal movement of the lower link in eitherdirection.

The device preferably includes a cam for automatically moving the outeredge of the lip upwardly simultaneously with its outward movement so asto clear the rear edge of the truck without any lifting of the lip bythe operator.

Another object is to provide a safer means of using the dock leveler byhaving the operator place the leveler in use from a position standingback on the dock instead of bending out over the edge of the dock.

It is accordingly among the objects of the invention to provide a lipextender for loading dock levelers having all of the advantages andbenefits of the invention set forth above and described in furtherdetail hereinafter in this specification.

Another object of the invention is to provide such a device which issimple and economical in its construction and operation.

Still another object of the invention is to provide such a device whichcan serve a secondary purpose of providing a block to prevent rollingstock from accidentially falling off the edge of the dock.

It is a further object of the invention to provide a device of the typedescribed which is adapted to be attached to and used with substantiallyevery edge-of-dock type dock leveler which is now in use.

Another object of the invention is to provide a means for holding thebridge plate and lip flat in order to prevent buckling and unwantedaccidental removal from the truck, which occurs with present state ofthe art levelers.

The invention also comprises such other objects, advantages andcapabilities as will later more fully appear and which are inherentlypossessed by the invention.

While there is shown in the accompanying drawings a preferred embodimentof the invention, it should be understood that the same is susceptibleof modification and change without departing from the spirit of theinvention.

DESCRIPTION OF THE DRAWINGS

FIG. 1 is a partial transverse sectional view of the dock leveler innormal out-of-use position;

FIG. 2 is a similar view showing the bridge plate and lip in elevated orcocked position;

FIG. 3 is a sectional view taken on line 3--3 of FIG. 2;

FIG. 4 is a sectional view taken on line 4--4 of FIG. 3;

FIG. 5 is a sectional view taken on line 5--5 of FIG. 3.

DESCRIPTION OF THE PREFERRED EMBODIMENT

The preferred embodiment of the invention is adapted for use withsubstantially any edge-of-dock type dock leveler now in use. Forpurposes of illustration, one type of conventional dock leveler is shownin the drawings, but the device is capable of being connected to andfunctioning with substantially all other types of dock levelers as well.

The conventional dock leveler structure includes a vertically directedbase plate 10, which is permanently fixed to the dock 11 and whichextends downwardly from the upper edge of the dock 11. A bridge plate12, which normally extends horizontally outwardly from the dock 11, ispivotally connected along one edge thereof to the upper edge of the baseplate 10 by a hinge 13.

The opposite edge of the bridge plate 12 is pivotally connected to oneedge of a lip 14, which normally hangs vertically downwardly from theouter edge of the bridge plate 12. The pivot connection between thebridge plate 12 and lip 14 comprises hinge means which includes a pintlepin 15. The pintle pin 15 preferably extends outwardly beyond one orboth side edges of the bridge plate 12 and lip 14 to provide aprotuberance which can be caught by the end of an elongated hook orchain device held by an operator for lifting purposes.

The structure of the present invention comprises a square lower plate 20which is welded or otherwise secured to the base plate 10 of the dockleveler. A pair of spaced parallel side plates 21 are welded orotherwise secured along one of their edges to the lower plate 20. Thelower plate 20 may be omitted and the side plates 21 welded directly tothe base plate 10.

An upper plate assembly is welded or otherwise secured to the lower sideof the lip 14 directly above the pintle pin 15. The upper plate assemblyincludes a pair of outwardly projecting side members 23, to each ofwhich is welded an angle iron clip 24 which is disposed at an angle withrespect to the side member 23 to which it is secured.

The clips 24 have threaded openings in the center of the portionsthereof which extend outwardly from the side members 23. A bolt 26 isthreadedly mounted in each of the openings for adjustment purposes. Theends of the bolts 26 are constructed and arranged to engage the underside of the bridge plate 12 when the mechanism is in cocked position.The bolts 26 are threadedly adjustable to control their length andthereby control the angular projection of the lip 14 as describedherinafter.

Mounted on the under side of the bridge plate 12 adjacent to the pintlepin 15 is a cam plate assembly which comprises a pair of angle iron sideplates 30 which are welded or otherwise connected to the bridge plate 12and to the opposite sides of a cam plate 31. The cam plate 31 extendstransversely with respect to the bridge plate 12 and its outer edgecomprises a curved cam surface 32 having at the lower end thereof aninwardly curved pocket or recess 33.

A lower link assembly comprises a lower link 34 having a pair of sides35 between which extend a pair of spaced angle iron reinforcements 36.The lower end of the link 34 is pivotally mounted on the shank of a bolt37, which extends through one of the side plates 21. The threaded innerend of the bolt 37 extends into one end of an elongated arbor 80, whichextends between the lower link 34 and the other side plate 21. A secondbolt 81 extends through the other side plate 21 and has its inner endthreaded into the opposite end of the arbor 80.

An elongated heavy duty coil spring 82 is mounted concentrically aroundthe arbor 80, as shown in FIGS. 3-5 of the drawings. One end 83 of thespring 82 extends upwardly and bears against the lowermost angle ironreinforcement 36 of the lower link 34. The other end 84 of the spring 82extends into the open end of a sleeve member 85. Threadedly extendingthrough the opposite end of the sleeve member 85 is an adjusting bolt86, the end of which bears against the lower plate 20.

The bolt 86 may be rotated to move the lower end of the sleeve 85 towardor away from the lower plate 20 and thereby adjust the amount of tensionwhich is exerted by the opposite end 83 of the coil spring 82 againstthe lower link 34.

Extending betwen the sides 35 at the upper end of the lower link 34 is abolt 38. A cam follower 39 is rotatably mounted on the bolt 38. The camfollower 39 is adapted to engage and follow the cam surface 32. Alsorotatably mounted on the bolt 38 is a spherical rod end 40, the rodportion 41 of which is threadedly connected to the lower part of thetoggle arm 42.

The upper end of the toggle arm 42 is rotatably journaled on a shaft 43which extends across the upper part of the upper plate assembly,extending through the side members 23.

A torsion spring 45 concentrically surrounds an arbor sleeve 46 mountedon the shaft 43. One end of the spring 45 engages the toggle arm 42 andthe other end engages the under side of the lip 14.

When the dock leveler is aligned in its normal out of use position, thebridge plate 12 extends horizontally and the lip 14 extends downwardlyin vertical position. Upon lifting movement exerted by the operator onthe end of the pintle pin 15 with a hook or the like, the bridge plate12 is pivoted upwardly on its hinge 13, carrying the lip 14 along withit.

It should be noted that the heavy duty coil spring 82 exerts pressureagainst the lower link 34 through engagement between the end 83 of thespring 82 and the angle iron reinforcement 36 of the lower link 34. Thespring 82 thereby exerts pressure which assists in lifting the weight ofthe bridge plate 12 and through the toggle arm 42 also assists inlifting the weight of the lip 14. The lip 14 customarily weighsapproximately 170 lbs. and the spring 82 helps to reduce the amount oflifting effort which must be exerted by the operator.

Upward movement of the lip 14 causes the lower link 34 to pivotrearwardly toward the dock 11, pivoting on the pivot pin 37. At the sametime, the toggle arm 42 also pivots rearwardly toward the dock 11,pivoting on the shaft 43.

When the bridge plate 12 approaches a substantially vertical position,lower link 34 and toggle arm 42 also reach substantially verticalaligned positions. Further upward movement of the pintle pin 15 causesthe lower link 34 and toggle arm 42 to move to an over-center positionin which they are inclined slightly toward the dock 11. The torsionspring 45 exerts pressure upon the toggle arm 42 to assure its movementinto an over-center position.

The device is now in what may be termed a cocked position, as shown inFIGS. 2 and 3 of the drawings. Movement beyond this position isprevented by engagement between the ends of the bolts 26 and the underside of the bridge plate 12 and by engagement between the cam follower39 and the cam surface 32. In this position, the cam follower 39 isdisposed within the recess 33 on the lower part of the cam surface 32.

The dock leveler is now in position for movement of the lip 14 into therear of the truck. This is accomplished by exerting downward and outwardpressure on the upper portion of the bridge plate 12 in the areaadjacent to the pintle pin 15. This may conveniently be done by the footof the operator.

As pressure is exerted against the upper portion of the bridge plate 12,the bridge plate 12 pivots forwardly, away from the dock 11. As thebridge plate 12 moves forwardly it causes the cam surface 32 to movedownwardly with respect to the cam follower 39. As the cam follower 39moves upwardly with respect to the cam surface 32, it also movesoutwardly due to the curvature of the cam surface 32. Upward and outwardmovement of the cam follower 39 is transmitted through the rod portion41 to the shaft 43, causing simultaneous upward and outward movement ofthe outer edge of the lip 14.

This upward and outward movement of the outer edge of the lip 14continues until the cam follower 39 approaches the upper end of the camsurface 32, at which time the toggle arm 42 and lower link 34 are movedout of their over-center position. They accordingly no longer supportthe bridge plate 12 and lip 14, which move to a horizontal position. Thecoil spring 82 provides pressure which resists but does not prevent thedownward movement of the bridge plate 12 and lip 14. The spring 82accordingly provides a counter-balancing effect during the downwardmovement.

In use, the truck which is disposed adjacent to the dock has a flathorizontal cargo carrying bed which is on a level with or disposedsomewhat above or below the level of the dock. The rear of the truckextends verticaly downwardly from a cargo carrying bed and is disposedonly a short distance outwardly from the edge of the dock. The lip 14 isdisposed vertically between the dock and the rear of the truck.

In using the dock leveler, it is necessary first to move the lipupwardly in such a manner that it will clear the rear of the truck. Thelip 14 must them be moved upwardly a sufficient distance to clear therear edge of the bed of the truck as the lip is moved into it. The bedof the truck may be disposed above the level of the dock or may have anelevated portion which is so disposed. The device is preferablyconstructed and arranged so that the outer edge of the lip is capable ofclearing a truck disposed approximately 6 inches above the level of thedock.

The device is provided with adjusting means for achieving the bestmovement of the lip. The lip adjusting bolts 26 control the distancebetween the outer edge of the lip 14 and the rear of the truck when theleveler is being moved into its cocked position. They may also beadjusted to provide maximum upward movement of the lip for maximumclearance over the truck bed. The rod portion 41 is adjustable withrespect to the upper plate 17 to control the height of the outer edge ofthe lip 14 when the toggle arm 42 and lower link 34 move into and out ofover-center position.

When the trust is loaded, it can be driven away from beneath the lip 14,which will drop down into its vertical out of use position. The lip 14and bridge plate 12 may also be removed from the trust by reversemovement of that described above.

Uppn such reverse movement, the coil spring 82 again acts to assist inthe lifting and reverse movement of the lip 14 and bridge plate 12 andcounter-balances their weight during such movement.

When the device is in cocked position it can be left in such elevatedcocked position and used as a block to prevent the accidental movementof rolling stock and /or personnel off the edge of the dock.

While the term "lower link" has been used to designate the lower link ortoggle member and the term "toggle arm" has been used to designate theupper link or toggle member, it should be understood that such terms arenot limiting and that any suitable pair of link or toggle members may beused which accomplishes the results shown and described.

We claim:
 1. A lip extender for use with a loading dock leveler of thetype having a vertically directed base plate, a bridge plate pivotallyconnected to said base plate and a lip pivotally mounted along its inneredge to the outer edge of the bridge plate, said lip extender comprisinga lower link pivotally connected at its lower end to said base plate, atoggle arm pivotally connected at its upper end beneath said lip, theopposite ends of said lower link and toggle arm being constructed andarranged so that upon lifting of said bridge plate, the pivotallyconnected ends of said lower link and toggle arm move into anover-center locking engagement with each other to hold said bridge plateand lip in an elevated position, and a cam mounted beneath said bridgeplate, said cam having a cam surface, a cam follower carried by thepivotal connection between said toggle arm and said lower link, and anelongated heavy duty coil spring disposed adjacent to the lower end ofsaid lower link, one end of said coil spring bearing against said baseplate and the other end of said coil spring bearing against the lowerend of said lower link to counter-balance the weight of said bridgeplate and lip through said lower link and toggle arm.
 2. The structuredescribed in claim 1, said coil spring being mounted directly adjacentto the pivotal connection between said lower link and said base plate.3. The structure described in claim 2, said coil spring being mountedaround an elongated cylindrical arbor, said arbor being aligned with anddisposed directly adjacent to the pivotal connection between said lowerlink and said base plate.
 4. The structure described in claim 3, saidlip extender having a pair of spaced side plates extending transverselyto said base plate, a shaft extending through said side plates, thelower end of said lower link being pivotally mounted about said shaft,said shaft extending through said arbor.
 5. The structure described inclaim 4, the end of said spring which bears against said base plateextending into one end of a hollow sleeve member, a bolt threadedthrough the opposite end of said sleeve member, said bolt beingadjustable to move the ehd of said spring toward or away from said baseplate to adjust the amount of tension exerted by said coil springagainst said lower link.
 6. The structure described in claim 5, andresilient means urging at least one of said lower link and toggle armmembers into said over-center relationship.
 7. The structure describedin claim 6, such resilient means urging said cam follower intoengagement with said cam surface.
 8. The structure described in claim 1,the end of said spring which bears against said base plate extendinginto one end of a hollow sleeve member, a bolt threaded through theopposite end of said sleeve member, said bolt being adjustable to movethe end of said spring toward or away from said base plate to adjust theamount of tension exerted by said coil spring against said lower link.9. The structure described in claim 1, said heavy duty coil springlocking said bridge plate and lip in flat extended position to preventsaid bridge plate and lip from buckling out of extended position.